For nearly three decades the fusing mechanism of choice for fixing toner images to paper or other surfaces has been a pair of pressure rollers. Generally, at least one of the rollers is heated and contacts the toner image to fuse it. A release liquid commonly called "fusing oil" is applied to the surface of one or both of the rollers to prevent the offset of toner onto the roller. The oil is commonly held in a reservoir from which it is pumped to a wick or other applicating mechanism. The oil in the reservoir must be replaced periodically.
A large variety of fusing oils are presently used in the industry. They vary both according to fusing application, for example, the temperature at which used, but more importantly according to their usefulness with the specific surface at which they are applied. Obviously, it is undesirable to have the wrong fusing oil in a particular apparatus. In addition to not working as well under the conditions of that fuser, it may also cause early replacement of an expensive roller.
The problem is especially serious when similar apparatus manufactured by a single manufacturer uses two different fusers requiring two different oils. For example, a black only version of an electrophotographic copier may use a particular fusing material requiring a particular oil and a more sophisticated color version of the same copier may require a different fuser utilizing a different oil. Getting the right oil for the right apparatus in this situation cannot be left entirely to directions on a package.
This problem can be approached by designing a separate oil bottle-reservoir system for each of the models. However, that requires tooling and manufacture of a separate reservoir for each of the models.